Lupus is a systemic autoimmune disease that occurs when your body's immune system attacks your own tissues and organs. Inflammation caused by lupus can affect many different body systems — including your joints, skin, kidneys, blood cells, brain, heart, and lungs.

Lupus can be difficult to diagnose because its signs and symptoms often mimic those of other ailments. The most distinctive sign of lupus — a facial rash that resembles the wings of a butterfly unfolding across both cheeks — occurs in many but not all cases of lupus.

Some people are born with a tendency toward developing lupus, which may be triggered by infections, certain drugs or even sunlight. While there's no cure for lupus, treatments can help control symptoms.

SYMPTOMS

No two cases of lupus are exactly alike. Signs and symptoms may come on suddenly or develop slowly, may be mild or severe, and may be temporary or permanent. Most people with lupus have mild disease characterised by episodes — called flares — when signs and symptoms get worse for a while, then improve or even disappear completely for a time.

The signs and symptoms of lupus that you experience will depend on which body systems are affected by the disease. The most common signs and symptoms include:

• Fatigue

• Fever

• Joint pain, stiffness and swelling

• Butterfly-shaped rash on the face that covers the cheeks and bridge of the nose or rashes elsewhere on the body

It appears that people with an inherited predisposition for lupus may develop the disease when they come into contact with something in the environment that can trigger lupus. The cause of lupus in most cases, however, is unknown. Some potential triggers include:

• Sunlight. Exposure to the sun may bring on lupus skin lesions or trigger an internal response in susceptible people.

• Infections. Having an infection can initiate lupus or cause a relapse in some people.

• Medications. Lupus can be triggered by certain types of blood pressure medications, anti-seizure medications and antibiotics. People who have drug-induced lupus usually get better when they stop taking the medication. Rarely do symptoms persist even after the drug is stopped.

RISK FACTORS

Factors that may increase your risk of lupus include:

• Your sex. Lupus is more common in women.

• Age. Although lupus affects people of all ages, it's most often diagnosed between the ages of 15 and 45.

COMPLICATIONS

Inflammation caused by lupus can affect many areas of your body, including your:

• Kidneys. Lupus can cause serious kidney damage, and kidney failure is one of the leading causes of death among people with lupus.

• Brain and central nervous system. If your brain is affected by lupus, you may experience headaches, dizziness, behaviour changes, vision problems, and even strokes or seizures. Many people with lupus experience memory problems and may have difficulty expressing their thoughts.

• Blood and blood vessels. Lupus may lead to blood problems, including anaemia and increased risk of bleeding or blood clotting. It can also cause inflammation of the blood vessels (vasculitis).

• Lungs. Having lupus increases your chances of developing an inflammation of the chest cavity lining (pleurisy), which can make breathing painful. Bleeding into lungs and pneumonia also are possible.

• Infection. People with lupus are more vulnerable to infection because both the disease and its treatments can weaken the immune system.

• Cancer. Having lupus appears to increase your risk of cancer; however, the risk is small.

• Bone tissue death (avascular necrosis). This occurs when the blood supply to a bone diminishes, often leading to tiny breaks in the bone and eventually to the bone's collapse.

• Pregnancy complications. Women with lupus have an increased risk of miscarriage. Lupus increases the risk of high blood pressure during pregnancy (preeclampsia) and preterm birth. To reduce the risk of these complications, doctors often recommend delaying pregnancy until your disease has been under control for at least six months.

Diagnosis

Diagnosing lupus is difficult because signs and symptoms vary considerably from person to person. Signs and symptoms of lupus may vary over time and overlap with those of many other disorders.

No one test can diagnose lupus. The combination of blood and urine tests, signs and symptoms, and physical examination findings leads to the diagnosis.